2,2',2"-Nitrilo[triethyl-tris-(3,3',5,5'-tetra-tert-butyl-1,1'-biphenyl-2,2 '-diyl) phosphite] is a compound having the formula I ##STR1##
This compound of formula I is useful as a processing stabilizer for organic polymers as taught in U.S. Pat. Nos. 4,318,845 and 4,374,219. The compound of formula I is disclosed as being a white powder melting at 121.degree.-134.degree. C. As such, the powdery product has defects in terms of handling and apparent density, exhibiting poor flowability, meterability, storage stability, hydrolytic stability and compatibility in polymeric substrates and lubricating oils.
It has now been found that the compound of formula I can be obtained in a different crystalline modification as purified crystalline particles which exhibit acceptable properties in respect to handling, apparent density, flowability, meterability, storage stability, hydrolytic stability and compatibility in polymeric substrates and lubricating oils.
The new modification is characterized by a novel crystalline form, melting in the range of 178.degree.-185.degree. C. as given by the peak temperature of the endotherm recorded by differential scanning calorimetry (DSC); and by an X-ray diffraction pattern obtained using Cu-K.alpha. which exhibits diffraction angles (2.THETA.) as seen below:
______________________________________ Peak No. Diffraction Angle ______________________________________ 1 5.4 2 6.3 3 8.8 4 9.9 5 10.3 6 10.8 7 11.7 8 13.8 9 14.8 10 15.5 11 16.1 12 17.0 13 17.7 14 18.4 15 20.2 ______________________________________
The instant invention also relates to a process for the preparation of this novel gamma crystalline modification of the compound of formula I.
The instant invention also pertains to a composition stabilized against thermal, oxidative and actinic induced degradation which comprises
(a) a polyolefin, and PA1 (b) an effective stabilizing mount (generally about 0.01 to about 5% by weight of the stabilized composition) of the gamma crystalline form of 2,2',2"-nitrilo[triethyl-tris-(3,3', 5,5'-tetra-tert-butyl-1,1'-biphenyl-2,2'-diyl) phosphite], characterized by melting in the range of 178.degree.-185.degree. C. and by an X-ray diffraction pattern obtained using a Cu-K.alpha. which exhibits diffraction angles (2.THETA.) as seen below:
______________________________________ Peak No. Diffraction Angle ______________________________________ 1 5.4 2 6.3 3 8.8 4 9.9 5 10.3 6 10.8 7 11.7 8 13.8 9 14.8 10 15.5 11 16.1 12 17.0 13 17.7 14 18.4 15 20.2 ______________________________________
Preferably, the polyolefin is polypropylene.
The process for the preparation of the gamma crystalline modification of the compound of formula I is crystallizing or recrystallizing the compound of formula I from an alkanol of 4 to 8 carbon atoms. Preferably the alkanol is an n-alkanol of 4 to 8 carbon atoms; most preferably 1-butanol or 1-octanol.
Some alkanols useful in the instant process are, for example, 1-butanol, sec-butyl alcohol, isobutyl alcohol, 1-pentanol, isoamyl alcohol, 1-hexanol, 2-ethyl-1-hexanol, 1-heptanol and 1-octanol.
Differential scanning calorimetry (DSC) measurements are obtained on a TA Instrument Inc., 910 differential scanning calorimeter, with a 100 mL/min nitrogen purge, aligned aluminum pan, temperature scan at 5.degree. C./min to 230.degree. C.
X-ray diffraction patterns are recorded on a Philips Norelco X-ray Diffractometer unit, using Cu-K.alpha. radiation with a nickel filter. All samples have a uniform particle size of 40 to 75 microns. This is the same particle size distribution obtained with the prior an compound of Example 3.